Chris is conducting reconnaissance on a remote target and discovers that pings are allowed through his target's border firewall. What can he learn by using ping to probe the remote network?

A. Which systems respond to ping, a rough network topology, and potentially the location of additional firewalls
B. A list of all of the systems behind the target's firewall
C. The hostnames and time to live (TTL) for each pingable system, and the ICMP types allowed through the firewall
D. Router advertisements, echo request responses, and potentially which hosts are tarpitted

Answer: A. Which systems respond to ping, a rough network topology, and potentially the location of additional firewalls